#!/usr/bin/env node
const { Readable }  = require('stream');

class MyReadable extends Readable{
  constructor(){
    super();
  }
  _read(){
    this.push(String.fromCharCode(this.#c++));
    if(this.#c>'z'.charCodeAt(0)) this.push(null);
  }
#c ='a'.charCodeAt(0);
}
let rs = new MyReadable();
rs.pipe(process.stdout);
